*{
    box-sizing: border-box;
}
.calc{
    width:234px;
    border:1px solid #000;
    border-radius: 10px;
}
.Calc-screen{
    background-color: #292a29;
    height: 80px;
    line-height: 80px;
    padding: 0 10px;
    font-size: 40px;
    text-align: right;
    color: #fff;
}
.calc button{
    background-color: #5e5f5e;
    display: inline-block;
    width: 25%;
    height: 50px;
    line-height: 50px;
    text-align: center;
    font-size: 24px;
    border-color: #000;
    border-style: solid;
    border-width: 0 1px 1px 0;
    color: #fff;
    cursor: pointer;
}
.calc button.zero{
    width:50%;
}
.calc button.ctrl{
    background-color: #3e3f3e;
}
.calc button.exp{
    background-color: #fd8d0e;
}